Rinse and drain the chickpeas under cold water. Chop the cucumbers, bell peppers, cherry tomatoes, and red onion into bite-sized pieces and arrange in a bowl.

In a small mixing bowl, whisk together lemon juice, olive oil, Dijon mustard, salt, and pepper. Add cayenne or red pepper flakes if desired.

In a large bowl, combine rinsed chickpeas with chopped vegetables. Pour dressing over and gently toss to combine.

Serve immediately or store in an airtight container, keeping the dressing separate until ready to serve for maximum freshness.